System for sealing an annular space in a wellbore

ABSTRACT

A system is disclosed for sealing an annular space between a tubular element ( 7 ) extending into a wellbore ( 1 ) and a cylindrical wall ( 1   b ) surrounding the tubular element, wherein a control line ( 18 ) for controlling a downhole device ( 12, 13, 14, 15 ) extends in longitudinal direction along the tubular element. The system comprises an annular seal layer ( 20 ) extending around the tubular element ( 7 ), the seal layer having an inner surface provided with a recess ( 40 ) for radially receiving the control line. The seal layer is provided with a longitudinal slit ( 31 ) defining a pair of opposite longitudinal edges ( 32, 34 ) which are movable relative to each other between an open position wherein the seal layer can be radially applied to the tubular element, and a closed position wherein the seal layer extends around the tubular element.

The present invention relates to a system for sealing an annular spacebetween a tubular element extending into a wellbore and a cylindricalwall surrounding the tubular element, wherein a control line forcontrolling a downhole device extends in longitudinal direction alongthe tubular element. In the field of hydrocarbon fluid production from awellbore it is generally required to seal the annular space formedbetween a production conduit extending into the wellbore and asurrounding casing or liner, or between the casing or liner and thewellbore wall. In such applications many times one or more control linesfor power transmission or signal transmission extend through the annularspace. Various packers have been applied to provide such sealingfunctionality. Some of these have terminal connections at either end forconnecting the control lines to the packers. Although such packers mayprovide adequate sealing capability, it has been experienced thatassembly of the packers and control lines to the tubular element at awell site can be difficult.

U.S. Pat. No. 6,173,788 discloses a packer for sealing an annular spacebetween a tubular element extending into a wellbore and a wellborecasing, wherein a control line for controlling a downhole device extendsin longitudinal direction through a recess formed in the outer surfaceof the packer. It is a drawback of the known system that the controlline needs to involve bends at both ends of the packer since the recessis radially displaced from the outer surface of the tubular element.Another drawback of the known system occurs if the tubular element isprovided with a plurality of the known packers mutually spaced along thetubular element. Generally such packers are pre-assembled to respectiveportions of the tubular element, termed “subs”, which are to beconnected to adjacent portions of the tubular element by threadedconnections. As a result, upon assembly of the tubular element, it mayoccur that the recesses of the respective packers become non-aligned.

It is an object of the invention to provide an improved system forsealing an annular space between a tubular element extending into awellbore and a cylindrical wall surrounding the tubular element, whichsystem overcomes the drawbacks of the prior art.

In accordance with the invention there is provided a system for sealingan annular space between a tubular element extending into a wellbore anda cylindrical wall surrounding the tubular element, wherein a controlline for controlling a downhole device extends in longitudinal directionalong the tubular element, the system comprising an annular seal layerextending around the tubular element, the seal layer having an innersurface provided with a recess for radially receiving the control line,the seal layer being provided with a longitudinal slit defining a pairof opposite longitudinal edges which are movable relative to each otherbetween an open position wherein the seal layer can be radially appliedto the tubular element, and a closed position wherein the seal layerextends around the tubular element.

It is thereby achieved that the control line can be extended along thetubular element before the seal layer is radially applied to the tubularelement thereby obviating the need to include bends in the control line.In case the tubular element is provided with a plurality of seal layers,it is furthermore achieved that the seal layers can be assembled to thetubular element such that the recesses of the respective seal layers aresuitably aligned with the control line.

It is to be understood that the control line can function to transmitsignals to or from the downhole device, for example to actively controlthe downhole device or to transmit measured signals, or to transmitpower to or from the downhole device.

Preferably the system further comprises fastening means for fasteningthe seal layer in the closed position thereof to the tubular element.

The system of the invention can suitably be applied in combination withan inflow control device for controlling inflow of fluid from the earthformation into the tubular element, wherein the control line is arrangedto control the inflow control device.

Suitably each seal layer includes a material susceptible of swellingupon contact with a selected fluid. Thus the seal layer is activated bycontact with the selected fluid (for example water or hydrocarbonfluid), which implies that it is no longer required to activate the seallayer by mechanical or hydraulic means. This is an important advantagesince such swelling seal layers can be made significantly longer thanconventional packers.

In a preferred embodiment the system of the invention includes aplurality of said seal layers and a plurality of said inflow controldevices, the seal layers and the inflow control devices being arrangedin alternating order along the tubular element. The annular space isthereby divided into a number of compartments whereby cross-flow offluid between different compartments is substantially prevented, andinflow of formation fluid from each compartment into the tubular elementis controlled by the respective inflow control device in communicationwith the compartment.

In order to prevent or reduce formation water bypassing each seal layerthrough the rock formation opposite the seal layer, it is preferred thatthe seal layer is significantly longer than a conventional packer. Forexample, in a preferred embodiment the length of the seal layersubstantially corresponds to the length of the respective tubular jointto which the seal layer is applied. In this respect it is to beunderstood that the seal layer suitably is assembled from a plurality ofshort seal layer sections positioned adjacent each other along thetubular joint. Seal layer sections having a length of between 0.5-2.0meter, for example about 1 meter, allow convenient handling on thedrilling rig floor.

The invention will be described in more detail hereinafter by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 schematically shows a wellbore in which an embodiment of aconduit and seal layer used in the method of the invention is applied;

FIG. 2A schematically shows a cross-sectional view of the conduit ofFIG. 1;

FIG. 2B schematically shows the seal layer before application to theconduit;

FIG. 3 schematically shows a longitudinal section of the seal layer whenapplied to the conduit;

FIG. 4 schematically shows a longitudinal section of seal layer whenapplied to the conduit; and

FIG. 5 schematically shows detail A of FIG. 4.

In the drawings like reference numerals relate to like components.

Referring to FIG. 1 there is shown a wellbore 1 formed in an earthformation 2 for the production of hydrocarbon fluid, the wellbore 1having a substantially vertical upper section 1 a and a substantiallyhorizontal lower section 1 b extending into a zone 3 of the earthformation from which hydrocarbon fluid is to be produced. The earthformation zone 3 is fractured whereby there is a risk that water fromother formation zones (not shown) enters the lower wellbore section 1 bvia fractures in formation zone 3. The upper wellbore section 1 a isprovided with a casing 4 cemented in the wellbore by a layer of cement5, and a wellhead 6 is arranged on top of the wellbore 1 at surface 7. Aproduction liner 7 extends from the lower end part of the casing 4 intothe substantially horizontal wellbore section 1 b. A production tubing 9provides fluid communication between the wellhead 6 and the productionliner 7, the production tubing 9 being suitably sealed to the productionliner 7 by packer 10.

The production liner 7 is provided with a plurality of inflow controldevices in the form of inflow control valves 12, 13, 14, 15 spaced alongthe length of the liner 7. Each inflow control valve 12, 13, 14, 15 iselectrically connected to a control center 16 at surface via a set ofcontrol lines 18 extending along the outer surface of the productionliner 7 and the inner surface of the casing 4, so as to allow eachinflow control valve 12, 13, 14, 15 to be opened or closed from thecontrol center 16.

A plurality of seal layers 20, 22, 24, 26 is arranged in the annularspace 28 between the production liner 7 and the wall of wellbore section1 b, wherein the seal layers 20, 22, 24, 26 and the inflow controlvalves 12, 13, 14, 15 are arranged in alternating order along theproduction liner 7. Each seal layer 20, 22, 24, 26 includes a materialsusceptible of swelling upon contact with water from a water-bearinglayer of the earth formation 2, such material preferably being HNBRelastomer.

Referring to FIGS. 2A and 2B there is shown a cross-section of theproduction liner 7 and the seal layer 20 before application of the seallayer to the production liner 7. The set of control lines 18 is enclosedby a cover member 30 which is fastened to the outer surface of theproduction liner 7 by suitable fastening means (not shown). The seallayer 20 has a longitudinal slit 31 defining a pair of oppositelongitudinal edges 32, 34 allowing the seal layer 20 to be movablebetween an open position (as shown in FIG. 2) in which said edges 32, 34are displaced from each other so as to allow the seal layer 20 to beradially applied in the direction of arrow 35 to the production liner 7,and a closed position (as shown in FIG. 3) in which said edges 32, 34are located adjacent each other so as to allow the seal layer 20 tosubstantially enclose the production liner 7. Furthermore, the seallayer 20 is provided with pairs of bores 36, 38 spaced at regularlongitudinal distances along the seal layer 20. The bores 36, 38 of eachpair are formed at the respective longitudinal edges 32, 34, and areformed so as to allow a bolt (referred to hereinafter) to be extendedthrough the aligned bores 36, 38 in order to fasten the seal layer 20 tothe production liner 7. The seal layer 20 is provided with alongitudinal recess 40 formed at the inner surface thereof foraccommodating the set of control lines 18 and the cover member 30.

In FIG. 3 are shown the production liner 7 and the seal layer 20 afterthe seal layer 20 has been radially applied to the production liner 7 soas to enclose the production liner 7. The seal layer 20 is clamped tothe conduit by a plurality of bolt/nut assemblies 42, each bolt/nutassembly 42 extending through a corresponding pair of the bores 36, 38.

Referring to FIGS. 4 and 5 there is shown the seal layer 20 and theproduction liner 7 in longitudinal section. The production liner 7 isassembled from a number of tubular joints 44 having a standard length ofabout 10 m (30 ft), whereby each seal layer 20, 22, 24, 26 extendssubstantially the full length of the respective tubular joint 44 towhich the seal layer 20 is applied. Each such joint 44 is provided withrespective connector portions 48 at opposite ends thereof forinterconnecting the various joints 44. The outer surface of the annularseal layer 20 is provided with a plurality of annular recesses 46regularly spaced along the length of the seal layer 20.

During normal operation, the production liner 7 is assembled from therespective tubular joints 44 and from respective short sections oftubular element (termed “subs”; not shown) which include the respectivecontrol valves 12, 13, 14, 15. Assembly occurs at the well site inprogression with lowering of the production liner 7 into the wellbore 1.The set of control lines 18 together with the cover member 30 is fed tothe production liner 7, and fixedly connected thereto, simultaneouslywith lowering of the production liner 7 into the wellbore 1. Each seallayer 20, 22, 24, 26 is then radially applied to the production liner 7at the desired location thereof in a manner that the recess 40 enclosesthe cover member 30 (and hence the control lines 18). The seal layer 20is then moved to its closed position so as to enclose the tubular joint44, and fixed to the tubular joint 20 by fastening the bolt/nutassemblies 42 extending through the respective pairs of bores 36, 38.The other seal layers 22, 24, 26 are assembled to the respective tubularjoints 44 in a similar manner. The production liner 7 is installed inthe wellbore 1 such that the seal layers 20, 22; 24, 26 and the inflowcontrol valves 12, 13, 14, 15 are located in the earth formation zone 3containing hydrocarbon fluid.

After the wellbore 1 has been suitably completed, hydrocarbon fluid isallowed to flow from earth formation zone 3 into the wellbore section 1a and from there via the inflow control valves 12, 13, 14, 15 into theproduction liner 7 and the production tubing 9. In the event thatformation water enters the annular space between the production liner 7and the wellbore wall, one or more of the seal layers 20, 22, 24, 26which become into contact with the formation water will swell untilfurther swelling is prevented by the wellbore wall. The annular recesses46 enlarge the contact area of the seal layers with formation water,thereby promoting swelling of the seal layers. Once the swollen seallayers 20, 22, 24, 26 become compressed between the production liner 7and the wellbore wall, further migration of the formation water throughthe annular space is prevented. In order to determine the location ofwater inflow, a test is carried by successively opening and/or closingthe inflow control valves 12, 13, 14, 15 and simultaneously measuringthe inflow of formation water. The location of inflow is determined froman observed reduced (or eliminated) inflow of formation water as aresult of closing of one or more specific inflow control valves 12, 13,14, 15. Once the location of water inflow has been determined, one ormore of the inflow control valve(s) 12, 13, 14, 15 at the location ofinflow are closed so that inflow of formation water into the productionliner 7 is thereby eliminated.

Swelling of each seal layer 20, 22, 24, 26 also results in adequatesealing of the seal layer against the production liner 7 and the covermember 30 so as to prevent fluid migration between the seal layer andthe production liner or the cover member 30.

Instead of allowing the seal layer to swell by virtue of contact withwater from the earth formation, such swelling can be triggered bybringing the seal layer into contact with water-base wellbore fluidpumped into the wellbore.

Furthermore, the seal layer can be made of a material susceptible ofswelling upon contact with hydrocarbon fluid, such as crude oil ordiesel. In such application the seal layer can be induced to swell uponcontact with hydrocarbon fluid produced from the wellbore. Alternativelythe seal layer can be induced to swell by pumping hydrocarbon fluid,such as diesel or crude oil, into the wellbore. The latter procedure hasthe advantage that premature swelling of the seal layer during loweringof the tubular element into the wellbore, is prevented.

Also, a hybrid system can be applied including seal layer sectionssusceptible of swelling upon contact with hydrocarbon fluid, and seallayer sections susceptible of swelling upon contact with water from theearth formation.

1. A system for sealing an annular space between a tubular elementextending into a wellbore and a cylindrical wall surrounding the tubularelement, wherein a control line for controlling a downhole deviceextends in longitudinal direction along the tubular element, the systemcomprising an annular seal layer extending around the tubular element,the seal layer having an inner surface provided with a recess forradially receiving the control line, the seal layer being provided witha longitudinal slit defining a pair of opposite longitudinal edges whichare movable relative to each other between an open position wherein theseal layer can be radially applied to the tubular element, and a closedposition wherein the seal layer extends around the tubular element. 2.The system of claim 1, wherein said downhole device is an inflow controldevice for controlling inflow of fluid from the earth formation into thetubular element.
 3. The system of claim 2, comprising a plurality ofsaid seal layers and a plurality of said inflow control devices, theseal layers and the inflow control devices being arranged in alternatingorder along the tubular element.
 4. The system of claim 1, wherein thetubular element is assembled from a plurality of tubular joints, andwherein the length of each seal layer substantially corresponds to thelength of the respective tubular joint to which the seal layer isapplied.
 5. The system of claim 1, wherein the seal layer is formed of aplurality of seal layer sections arranged adjacent each other.
 6. Thesystem of claim 1, wherein said cylindrical wall is the wall of thewellbore.
 7. The system o claim 1, wherein each seal layer comprises i amaterial susceptible of swelling upon contact with a selected fluid. 8.The system of claim 7, wherein the seal layer comprises an elastomermaterial susceptible of swelling upon contact with water from the earthformation.
 9. The system of claim 8, wherein the seal layer comprisesHNBR elastomer.
 10. The system of claim 7, wherein the seal layercomprises a plurality of annular recesses formed at the outer surface ofthe seal layer and regularly spaced in longitudinal direction.
 11. Thesystem of claim 1, further comprising fastening means for fastening theseal layer in the closed position thereof to the tubular element. 12.The system of claim 1, wherein a cover member covers the control lineand wherein the recess is adapted to radially receive the cover member.13. (canceled)